The invention is directed to a process for the production of carboxylic acid cyanides, e.g., acyl cyanides by reaction of a carboxylic acid halide with an alkali metal cyanide or hydrogen cyanide in the presence of a copper (I) salt and a carboxylic acid nitrile.
It is known to produce carboxylic acid cyanides from carboxylic acid halides by reacting the halides in the presence of catalytic amounts of copper (I) cyanide, copper (II) cyanide, zinc cyanide or their complex compounds with alkali cyanides or hydrogen cyanide at a temperature of 100.degree. to 300.degree. C. (German AS No. 2614242 and related Findeisen U.S. Pat. No. 4,143,068, the entire disclosure of the Findeisen U.S. patent being hereby incorporated by reference and relied upon). The disadvantage in this process is that to produce suitable transformations relatively high temperatures, chiefly above 200.degree. C., and/or long reaction times are needed. However, side reactions are favored under these conditions, especially the formation of dimers so that the yields are moderate. With certain carboxylic acid cyanides, for example, with the lower aliphatic carboxylic acid cyanides, the yields only amount to a few percent.
It is also known to carry out the reaction of the carboxylic acid halide with an alkali metal cyanide in the presence of a copper (I) salt and a carboxylic acid nitrile, especially acetonitrile and thereby to operate at a temperature from 50.degree. to 180.degree. C. (German OS No. 2708182 and related Klenk U.S. Pat. No. 4,108,875, the entire disclosure of which is hereby incorporated by reference and relied upon). It is true that in this process relatively low temperatures are sufficient; however, the reaction times are undesirably long and the yields of carboxylic acid cyanide are not satisfactory.